Postoperative Assessment and Management of Obesity Surgery

Anatomy and Physiology

The stomach is divided into 4 anatomical regions:

• Cardia: Located just below the gastroesophageal junction
• Fundus: Dome-shaped area adjacent to the cardia
• Body: The central, largest part beneath the cardia and fundus
• Pylorus: Begins at the angular notch between the body and pylorus, including the antrum, canal, and sphincter, and connects to the small intestine at the L1 vertebra

Curvatures

• Greater curvature
  • Starts at the cardiac notch and curves along the lateral border of the fundus, body, and pyloric antrum
  • Supplied by the short gastric and right and left gastroepiploic arteries
• Lesser curvature:
  • Extends from the gastroesophageal junction along the medial surface to the angular notch
  • Supplied by the left gastric artery (from the celiac trunk) and the right gastric artery (from the hepatic artery)

Blood Supply

The stomach receives its arterial blood supply from an extensive anastomotic network originating from the celiac trunk and its branches:

• Right gastric artery: Branches from the common hepatic artery, which itself branches from the celiac trunk
• Left gastric artery: One of the 3 primary branches of the celiac trunk
• Right gastroepiploic artery: Arises from the gastroduodenal artery, a branch of the common hepatic artery
• Left gastroepiploic artery: Branches from the splenic artery, which is a branch of the celiac trunk

Venous Drainage

The stomach's veins mirror the arteries:

• Right and left gastric veins: Drain directly into the hepatic portal vein
• Short gastric and gastroepiploic veins: Drain into the superior mesenteric vein

Innervation

• Parasympathetic supply: Provided by the vagus nerve (10th cranial nerve)
• Sympathetic supply: Provided by the greater splanchnic nerve, which originates from the T6–T9 spinal segments

Physiology of Digestion

Digestion: The stomach processes food both mechanically and chemically through churning and the secretion of enzymes and acid. The three muscular layers of the stomach mix and churn food into chyme.

• Gastric acid secretion: Parietal cells in the oxyntic area secrete hydrochloric acid, creating an acidic environment that converts pepsinogen to pepsin, an enzyme that digests proteins.
• Gastric emptying: Chyme is released into the duodenum through the pyloric sphincter, which permits only liquids and small particles to pass.
• Vitamin B12 absorption: This intrinsic factor, produced by the stomach, is crucial for vitamin B12 absorption.
• Protection from self-digestion: Goblet cells produce mucus to shield the stomach lining from self-digestion.

Indications

Although nonsurgical interventions are often attempted first, failure of medication is not required to qualify for weight-loss surgery. Both nonsurgical and surgical interventions can be pursued concurrently, with medication potentially starting during the preoperative evaluation.

The following are indications for bariatric surgery:

• Body mass index (BMI) ≥40 kg/m²
• BMI ≥35 kg/m² with severe comorbidity (eg, type 2 diabetes, hypertension, obstructive sleep apnea)
• BMI ≥30 kg/m2 with resistant type 2 diabetes, high blood pressure, severe sleep apnea, or metabolic syndrome
• Medically cleared to undergo anesthesia and surgery
• Committed to long-term follow-up

Contraindications

There are no absolute contraindications to bariatric/obesity surgery, but there are some relative contraindications. These include:

• Severe heart or lung diseases (severe heart failure, end-stage lung disease, portal hypertension, and unstable coronary artery disease)
• Active substance use disorder, including alcoholism, drug/alcohol dependency, or a history of substance use within the previous year
• Cirrhosis, chronic pancreatitis, advanced cancer, and active cancer treatment
• Major depression, other uncontrolled mental health problems, or impaired intellectual capacity
• Crohn disease (if a laparoscopic Roux-en-Y gastric bypass [RYGB] procedure is planned).

Moreover, bariatric surgery is performed under general anesthesia, so any contraindication to receiving general anesthesia is relative to bariatric/obesity surgery.

Equipment

In robotic surgery, a small 3-dimensional camera is placed into the abdominal cavity. Robotic-controlled arms then manipulate various instruments, such as scissors, graspers, and staplers, which are inserted into the abdomen through small incisions.

 Equipment for a laparoscopic RYGB includes the following:

• Orogastric tube
• Nathanson liver retractor
• For access: Scalpel with no. 11 blade, Langenbach retractors, artery clips
• A 30-degree laparoscope with a light source and monitor
• Gas insufflation equipment
• Hasson trocars: 5 mm and 10 to 12 mm ports
• Three bowel-safe graspers
• Laparoscopic ultrasonic dissector (eg, harmonic scalpel)
• Electrocautery equipment
• Laparoscopic suction irrigator
• Laparoscopic clips
• Medium wound protector
• Laparoscopic linear cutting stapler [2]

Preparation

In the 3 weeks before surgery, the following dietary modifications can be made:

• Reduced calories: Carbohydrates (especially refined sugars in candy and soft drinks) should be reduced.
• Increased protein intake: The goal should be 60 or more grams of protein daily from sources such as chicken, lean ground beef, eggs, and salmon.
• Healthy fat intake: Healthy fats from fish, nuts, and olives should be consumed while avoiding trans fats and fats from butter and oils.
• Hydration: Plenty of water should be consumed (soft drinks and alcohol should be avoided).

Most programs suggest consuming 800 to 1200 calories daily and following these guidelines until 2 or 3 days before gastric sleeve surgery.

Technique or Treatment

Weight loss therapy can be divided into either surgical or conservative treatments. The latter refers to behavioral modification in the form of increased physical activity and alterations in diet. While this usually leads to an average of 10% short-term weight loss, it is difficult for patients to maintain. Surgical weight loss has been defined as the most effective and long-lasting form of weight reduction.[3] According to the National Institutes of Health, candidates for bariatric surgery include those with a BMI of 40 kg/m² or higher or a BMI of 35 kg/m² or higher in the setting of comorbidities.[1] 

Surgical Obesity Treatment

There are different types of surgical obesity treatment: malabsorptive and restrictive procedures, or a combination of both. Malabsorptive surgeries prevent the absorption of food and restrict calories by reducing the volume of food intake due to early satiety.[4] The 4 most commonly performed bariatric surgeries include the adjustable gastric band, sleeve gastrectomy, RYGB, and the biliopancreatic diversion, also known as the duodenal switch.

Adjustable gastric band

The adjustable gastric band procedure is typically performed laparoscopically. This is a restrictive procedure, meaning weight loss is induced by reducing the food consumed.[5] While losing popularity, it is still appealing to some patients because it is reversible, and the band is easy to adjust for more (or less) weight loss. Patients request this surgery because there is no bowel anatomy rearrangement, cutting, or dividing of the intestine. This procedure has a low complication rate but is also found to have less successful long-term weight loss than other types of bariatric surgery. 

The surgery involves placing a band around the proximal stomach, approximately 2 cm below the esophagogastric junction, to create a small, approximately 15 mL pouch.[4] The band is attached to a subcutaneous port placed on the anterior rectus sheath, inflating it like a balloon.[4][6] The goal is for patients to feel full sooner and longer due to decreased space for food and slower emptying. The desired weight loss is 1 to 2 pounds (0.5–1 kg) per week, and it can be titrated by filling (or emptying) the lap band around the proximal stomach.[5][6]

Sleeve gastrectomy

Another bariatric surgery that falls into the restrictive category is sleeve gastrectomy.[5] This procedure is performed laparoscopically, and due to its low rate of complications and reoperations, it is the most common bariatric surgery performed worldwide.[7] This procedure is often the one chosen by high-risk individuals with a BMI greater than 60 and may be performed as a prequel to a duodenal switch or RYGB.[3] The surgical technique involves the removal of 80% of the stomach, starting at 4 to 6 cm from the pylorus and extending along the greater curvature to the angle of His.[6][7] The result is an approximately 100 mL gastric tube allowing limitation of food intake with preservation of the pylorus—no anastomosis is required.[3][6][7]

Roux-en-Y gastric bypass 

Combining both restrictive and malabsorptive aspects of weight loss surgery, RYGB is another common bariatric surgery. This procedure involves the (laparoscopic) creation of a 20 to 30 mL gastric pouch using the cardia of the stomach, separating it from the remaining stomach, pylorus, and proximal small bowel.[8] Measuring 40 cm from the ligament of Trietz, the jejunum is divided and brought up in an antecolic or retrocolic fashion and anastomosed to the stomach pouch. This alimentary or "roux" limb is then traced distally, 75 to 100 cm, where an entero-enterotomy is created between it and the biliopancreatic or "Y" limb that drains the proximal small bowel and accessory organs. After this, potential spaces within the mesentery are closed to prevent internal hernia.[9] 

Biliopancreatic diversion/duodenal switch

Biliopancreatic diversion with duodenal switch (BPD/DS) is a less commonly performed bariatric surgery that combines restrictive and malabsorptive components. These result in the greatest weight loss but also have the greatest postoperative mortality, at a rate of 1.1%.[10][11] They are technically more challenging for the surgeon and may be performed open or laparoscopically. BPD begins with a distal gastrectomy and closure of the duodenal stump. The ileum is transected, brought up, and anastomosed to the stomach pouch as an alimentary/Roux limb.

Further, an ileo-ileostomy is formed between the alimentary ileal limb (approximately 250 cm distal to the stomach) and the proximal ileum (continuous with biliary/pancreatic drainage), resulting in a 50 to 100 cm common channel before emptying into the colon. The duodenal switch begins similarly to a sleeve gastrectomy, forming a gastric pouch based on the lesser curvature. The duodenum is transected approximately 4 cm distal to the pylorus, and this is anastomosed to the ileal alimentary limb. Allowing approximately 250 cm of alimentary limb, an ileo-ileostomy is performed roughly 100 cm from the ileocecal valve, creating a common channel similar to BPD.

Postoperative Care Following Bariatric Surgery

Performing bariatric surgeries laparoscopically has been a trend as the technique is associated with decreased hospital length of stay, wound complications, postoperative pain, and improved surgical cosmesis. Furthermore, laparoscopic surgery reduces the risk of postoperative venous thromboembolism (VTE), which has been identified as a frequent cause of postoperative morbidity and mortality. With that being said, all patients are placed on an aggressive VTE prevention regimen following surgical intervention. Early ambulation (within 4–6 hours after surgery), sequential compression devices, and pre- and postoperative low molecular weight or unfractionated heparin are essential.[12]

Regarding oral intake, patients typically start on a clear, bariatric diet within the first 24 hours postoperatively as long as they tolerate water and there are no clinical signs of staple line or anastomotic leak.[13] Once tolerating a low-fat, full-liquid diet and ambulatory, patients are discharged home with protein supplements, a vitamin regimen, and gradual progression in food consistency over the next several months. Outpatient follow-up typically involves postoperative visits between 2 and 6 weeks and check-ups at 3 and 6 months. Subsequently, patients are examined biannually for 2 years and annually thereafter.[8] Patients are encouraged to increase physical activity once they have recovered from surgery, as this limits the loss of lean tissue, decreases the risk of regaining weight, and encourages cardiovascular health. Strength training and aerobic exercise are encouraged for at least 30 minutes daily, and increased activity is incorporated into daily behaviors.[5]

Nutritional Consequences of Bariatric Surgery

As patients continue to thrive at home following surgery, their diet is advanced to solids with a goal of approximately 1200 calories and 60 to 120 grams of protein per day. While protein malnutrition is rare following bariatric surgery (except BPD/DS), many patients experience intolerance to protein-dense foods and should be monitored for such. Vitamin supplementation is also recommended upon discharge, and patients are often provided multivitamin regimens, including additional iron, calcium, vitamin D, and vitamin B, with routine monitoring and further customization of supplements based on the patient’s labs and clinical status.[7] Importantly, patients may also experience dietary complications such as dehydration, steatorrhea, dumping syndrome, and chronic nausea and vomiting as a consequence of the anatomic alterations seen with bariatric surgery.[6][13]

As mentioned previously, the vitamin deficiencies seen after weight loss surgery include iron (33%–55% of patients), calcium and vitamin D (24%–60%), vitamin B12 (24%–70%), and thiamine (<5%). Following RYGB, the most frequent nutritional deficiencies are iron and B12 depletion, seen in up to 60% and 70% of patients, respectively. Iron deficiency is due to the duodenum and proximal jejunum being bypassed, as they both serve as iron absorption sites. B12 is typically absorbed within the terminal ileum after binding with intrinsic factor, a substance secreted by the parietal cells of the gastric antrum. Resecting the gastric antrum during RYGB delays mixing intrinsic factor and B12, resulting in poor absorption at the terminal ileum.[8] Treatment of iron and B12 deficiencies includes oral supplementation, which may be escalated to the intravenous route if needed.[5][8]

Restrictive procedures, such as sleeve gastrectomy, can put patients at higher risk for dehydration due to early satiety. As such, patients are instructed to take sips of liquids throughout the day. Regarding malabsorptive procedures, patients may have the unpleasant side effects of increased flatulence, bloating, and loose, foul-smelling stools due to fat and starch malabsorption.[13] These patients are also more likely to have fat-soluble vitamin deficiencies (vitamin A deficiency in 69% of patients and vitamin D deficiency in 63%) and protein-calorie malnutrition—especially after BPD or DS. 

Overall, 30% of patients experience dumping syndrome, a form of rapid gastric emptying associated with RYGB and BPD that occurs secondary to high-sugar gastric content "dumping" into the small bowel associated with pyloric discontinuity. Blood is shunted to the mesentery as highly concentrated liquid enters the small bowel. Signs of dumping syndrome include nausea, abdominal discomfort, diarrhea, and vasomotor symptoms such as flushing, diaphoresis, and heart palpitations. Treatment involves diet modification with small, frequent meals throughout the day, limiting liquids with meals, increasing fiber intake, and avoiding simple sugars. Lastly, roughly 4% of post-bariatric surgery individuals experience frequent nausea and vomiting. In addition to being worked up for the possible anatomic cause of symptoms, patients should be monitored closely for signs of Wernicke encephalopathy (neuropathy, myopathy, encephalopathy), which occurs due to thiamine deficiency and can be treated with oral or intravenous replacement.

Anticipated Weight Loss

Following bariatric surgery, patients can expect to see the largest drop in weight within the first year, with the most rapid weight loss occurring within the first 3 months. Patients commonly regain approximately one-third of their initial weight loss over the subsequent 2 to 6 years; however, weight typically stabilizes between 6 and 15 years following surgery.[5] In general, interventions that involve less gastrointestinal tract rearrangement (ie, restrictive procedures) tend to result in less weight reduction; however, these patients also experience fewer long-term and perioperative problems.

Most weight is shed after BPD/DS, which has been reported to result in up to 83% of excess weight lost (EWL) at 3 years.[11] RYGB follows, with 77% EWL at 1 year and a 30% to 35% reduction in total body weight at 1 to 3 years. While it is apparent that weight reduction is greater following malabsorptive procedures, sleeve gastrectomy still maintains an EWL of 57.6% at 1 year and 73.8% EWL overall.[3][5][7] As for adjustable gastric banding, although it is considered the least invasive bariatric procedure, total body weight reduction at 3 years is reported to be only 15.9%.[6]

Complications

Despite the optimization of surgical techniques and postoperative care, it is still imperative for clinicians and surgeons to monitor bariatric individuals for both medical and surgical complications and treat them accordingly. Overall 30-day mortality among all patients undergoing bariatric surgery is less than 1%, with restrictive procedures being 0.1%, RYGB 0.5%, and 1% for BPD/DS.[6] Serious complications are seen in roughly 4% of patients. They are more pronounced in patients with high BMI, history of venous thromboembolism (VTE), obstructive sleep apnea, and inability to ambulate at least 200 feet in the preoperative setting.

Older patients who use tobacco and present with multiple comorbidities have an increased risk of postoperative complications.[6] Nutrition complications aside, bariatric surgery has been associated with medical complications such as VTE (0.3%), marginal ulcers, cholelithiasis, nephrolithiasis, urinary tract infections (0.3%), and wound infections (0.5%). Surgical complications include a staple line or anastomotic leak (0.2%), bleeding (0.7%), intestinal obstruction or internal hernia, and anastomotic stenosis.[6][14]

As VTE is a common cause of morbidity and mortality following bariatric surgery (0.3% at 7 days and 2% at 180 days), it is important to note modifiable and nonmodifiable risk factors.[15] From a patient perspective, increased BMI and age (older than 50), male sex, smoking, or VTE history increase the risks.[12][15] Surgeons can prevent VTE in their patients by maintaining operative time of less than 3 hours, using minimally invasive techniques, and taking all measures possible to avoid staple line and anastomotic leaks and revisional surgery. When deciding on surgery, it is important to note a higher association of VTE with malabsorptive procedures vs restrictive ones.[12] Any patient with a suspected pulmonary embolism (ie, tachycardia or shortness of breath) should have a prompt computed tomography (CT) scan and be anticoagulated if a pulmonary embolism is identified.[13]

From a surgical perspective, anastomotic or staple line leaks and bleeding have been identified as having the greatest association with sepsis, reoperation, and intensive care unit admission.[14] A leak can be difficult to identify clinically, as obese individuals may not present with peritonitis or even fever, as would be expected of other patients. Sometimes, the only warning sign is tachycardia.[13] If suspected, investigation via CT must proceed immediately, as early intervention can save lives; however, routine imaging is not recommended if patients are free from symptoms.[13][16] Treatment includes operative or image-guided drainage, antibiotics, total parental nutrition, and endoscopic stenting across the leaking staple line.[3][13]

Internal hernias are identified in 1% to 3% of patients undergoing RYGB or BPD/DS and are more commonly seen after patients begin to lose weight.[13] Patients may present with postprandial abdominal discomfort associated with intermittent nausea/vomiting or with outright signs and symptoms of bowel obstruction. Diagnosis via CT or upper gastrointestinal series demonstrates dilated bowel loops, mispositioning, and engorgement of mesenteric vessels. Internal hernias are noted within the transverse colon mesenteric defect in 69% of patients, between the mesentery of the Roux limb and transverse mesocolon (aka Peterson defect) in 18%, and at the entero-enterostomy mesenteric defect in 13%.[1][13] Treatment includes prompt exploration (laparoscopic preferred) with a hernia reduction and closure of the defect. Unfortunately, 4.7% of these patients require bowel resection, and there is a 1.17% mortality associated with the diagnosis of internal hernia.   

Stenosis and marginal ulcers usually manifest at the gastroenteric anastomosis. Stenosis is seen more than 30 days postoperatively, and patients present with epigastric pain and regurgitation. Diagnosis and treatment include endoscopy with balloon dilation of the anastomotic site.[13] Marginal ulcers may present with epigastric abdominal pain or hematemesis and are also diagnosed via endoscopy. Treatment includes proton pump inhibitors and avoidance of nonsteroidal anti-inflammatory drugs.[5][13]

Complications Based on Type of Bariatric Surgery

Adjustable gastric band

Adjustable gastric banding is associated with the lowest postoperative morbidity and mortality rates among bariatric procedures, with a 30-day mortality ranging from 0% to 0.1%.[6][15] When performed laparoscopically, the procedure carries an approximately 1% risk of major complications, with a long-term complication rate of about 2% per year.[6] The most commonly seen complications involve erosion of the band into the gastric wall, port-related difficulties such as infection, and band slippage with herniation of the stomach, resulting in obstruction and esophageal dilation.[6] Band erosion is seen in 0.3% to 7% of patients and is diagnosed via upper endoscopy or upper gastrointestinal series. Treatment involves surgical removal of the band and repair of the stomach.[13]

Band slippage and subsequent gastric outlet obstruction are diagnosed in patients who have developed food intolerance or new/worsening reflux.[4] A plain radiograph may reveal the band in a horizontal (10 to 4 o’clock) position or evidence of an obstruction on the upper gastrointestinal study.[4][13] Treatment involves deflation of the band, insertion of a nasogastric tube with pouch decompression, and surgical removal of the band or replacement/repositioning. The latter method has been found effective in 89% of patients in short-term follow-up.[4] As previously mentioned, adjustable gastric banding has the lowest risk of postoperative morbidity and mortality, including the smallest risk of VTE.[12][15] Unfortunately, while AGB has the lowest morbidity and mortality, it also demonstrates the least long-term weight loss among all bariatric surgeries.[6]

Sleeve gastrectomy

As discussed, sleeve gastrectomy complications are rare, with a global rate of 7.7%.[3] The most feared impediments, other than death (30-day mortality is 0.5%), include staple line leak, bleeding, and sleeve narrowing or stenosis. Leaks are most commonly seen in the proximal third of the stomach near the angle of His at a frequency of roughly 3.3%.[3][13]

Roux-en-Y gastric bypass

The 30-day postoperative mortality for RYGB is 0.2% to 0.5%.[6][15] Of those deaths, VTE is found to be the cause in 20% to 30%, and it is seen in roughly 0.5% of patients postoperatively. Other early complications of RYGB include anastomotic leak (1%) and cardiac event in 0.2% to 1% of patients.[13] Late surgical events are small bowel obstruction due to internal hernia (1%–3%), stenosis of the gastro-jejunal anastomosis (3%–12%), and marginal ulcers (0.5%–20%).[1][13] Laparoscopic RYGB is preferred over open due to decreased risk for complications (4.8% vs 7.8%), VTE, and mortality (0.2% vs 2%). However, the laparoscopic procedure does have a higher risk of internal hernia (2.5%) compared to open.[1][6][12]

Biliopancreatic diversion/duodenal switch

BPD and DS are accompanied by the most weight loss but also by the highest morbidity and mortality rates.[6][10][11] The 30-day mortality has been cited at 1.1%, and major complications occur in approximately 3% of cases.[10][15] Depending on the technique, anastomotic leaks and strictures are seen in up to 2.6% and 10% of patients, respectively. Similar to RYGB, marginal ulcers are associated with BPD but are unlikely in DS due to pyloric preservation.[10]

Clinical Significance

After discussing the complications associated with bariatric surgery, the decision to proceed with surgical intervention may seem intimidating to patients. Notably, obesity is an independent risk factor for health conditions, including stroke, coronary artery disease, obstructive sleep apnea, hyperlipidemia, diabetes mellitus, hypertension, degenerative joint disease, asthma, cancer, and depression.[11] Obesity is a major health concern worldwide and is associated with decreased life expectancy, quality of life, and higher healthcare costs.[7] Bariatric surgery is the most effective approach for weight loss and has been proven to reduce the severity of (or eliminate) many of the comorbidities and causes of death associated with obesity.[6][7][12]

Improvement in comorbidities is noticed as early as 6 months following weight loss surgery. Patients have improved longevity with an 80% drop in annual mortality and a 50% reduction in overall mortality.[11][17] Not only has the incidence of stroke and myocardial infarction decreased, but obstructive sleep apnea has also improved or resolved in 85.7% of patients. After BPD and DS, 99.1% of patients had improvement in hyperlipidemia. All patients undergoing surgery demonstrated lower levels of low-density lipoprotein and triglycerides.[6][11] Recovery of type 2 diabetes was also observed, and 76.8% of patients had complete resolution—again, more prominent following malabsorptive procedures. Furthermore, all patients who underwent surgery demonstrated improved blood pressure, and hypertension was cured in 61.7%.[11]

Enhancing Healthcare Team Outcomes

Considering all the behavioral, bodily, and lifestyle changes associated with weight loss procedures, it is no surprise that the psychological care of a bariatric individual plays a major role in both the pre-and postoperative setting. Preoperative psychological evaluation is advised to ensure patients are prepared for such a dramatic undertaking. Patients experiencing a major depressive disorder, substance use disorder, or binge eating disorder may require further psychiatric care or even be disqualified from surgery.[6] Once deemed emotionally prepared for surgery, patients are encouraged to attend support groups throughout the perioperative period.[5] 

Even considering the physical and emotional stress associated with bariatric surgery, most patients experience an improved quality of life by enriching their psychosocial functioning, mood, self-image, and perceived health. In addition, patients have superior mobility and reduced anxiety, which translates into expanded confidence and interaction with others, ultimately resulting in amplified productivity and economic opportunities.[5][11] While bariatric surgery has known medical, surgical, and nutrition-related complications, it has been proven to positively affect patients' longevity, comorbidities, and quality of life.

A team of surgeons, internists, dieticians, psychologists, and a strong emotional support group is essential for optimal outcomes following weight loss surgery. Close monitoring can identify and remediate surgical, medical, and nutritional complications with minimal sequelae. With continued psychological support, patients are prepared for lifestyle changes that aid in successful weight loss and improved confidence and productivity. With appropriate preoperative selection and diligent postoperative monitoring, patients undergoing bariatric surgery can experience significant and sustained benefits from weight loss procedures.